Organic flocculants have, in recent years, received considerable attention as replacements for inorganic flocculants. The reason is, as mentioned in U.S. Pat. No. 4,155,847, that even though inorganic flocculants (e.g., aluminum sulfate, polyaluminum chloride, ferrous sulfate and ferric chloride) are less expensive than organic flocculants, their use involves several disadvantages. Generally, inorganic flocculants must be used in large amounts, often several times the amount of organic flocculants. When used in sludge treatment, after concentration and dewatering, the sludge will contain large amounts of metal oxide or metal hydroxide even after further treatment, such as burning. This results in production of large quantities of ash with its concomitant disposal problem.
The aforementioned U.S. Pat. No. 4,155,847 discloses cationic flocculants which are water-soluble polycondensates of epihalohydrin and amines. These flocculants are said to be useful for flocculation of various types of suspensions such as, for example, industrial waste waters and pulp slurry obtained in paper making. The flocculants described in the patent, however, are not lignin based products.
U.S. Pat. No. 3,784,493 discloses the Mannich reaction products of acidified spent sulfite liquor with amines (both monoamines and polyamines) and formaldehyde. The resulting products are stated to be useful as setting control agents for cements, hydration shale inhibitors and fillers for resins.
U.S. Pat. No. 4,017,419 describes cationic bitumin or asphalt emulsions stabilized with polyamine-lignin reaction products.
U.S. Pat. No. 4,017,475 describes high molecular weight flocculating agents obtained by reacting lignosulfonate or spent sulfite liquor with phenol, followed by the reaction of the hydroxyphenylated lignosulfonate with ammonia, primary amines or secondary amines.
Other patents of interest include U.S. Pat. Nos. 2,581,035; 2,709,696; 2,731,425; 2,859,186; 2,863,780; 3,538,071; 3,671,428; 3,697,497; 3,871,893 and 3,912,706. While this list is by no means exhaustive, it is representative of efforts of the prior art workers in this field. So far as it is known, however, there is still a need for a truly effective economical organic flocculant today which meets the ever increasing industrial demand. This invention, therefore, is aimed at providing a novel and effective organic flocculant which satisfies long felt industrial requirements for efficient and economical flocculating agents.
Accordingly, it is an object of the present invention to provide novel and improved organic cationic flocculants obtained by reacting kraft lignin with aldehydes and polyamines.
It is also an object of this invention to provide such organic cationic flocculants which are useful for the removal of suspended solids from waste water and the like.
The foregoing and other objects of this invention will become more apparent from the ensuing detailed description and the several examples.